Insulating glazing units (IGUs) comprise two or more glass lites (panes) separated by one or more volumes which are sealed and then filled with an insulating gas mixture and/or partially evacuated to create at least one insulating cavity. Vacuum insulating glazing units (VIGUs) comprise two or more glass lites separated by one or more volumes which are sealed and evacuated to create at least one insulating vacuum cavity. The volume between the lites is sealed around its perimeter (or edge) by an edge seal. The edge seal is a part (or assembly of parts) that is bonded to one lite, spans across the gap between the two lites, and is bonded to the second lite. At any time after the IGU/VIGU has been assembled, the first lite may have a difference in temperature from the second lite. The temperature difference leads to differential expansion or contraction and, therefore, relative motion between the glass lites. A rigid edge seal strongly resists the relative motion between the lites, thereby creating a buildup of thermal stresses within the IGU/VIGU assembly. A need therefore exists, for a compliant edge seal that permits relative motion between the glass lites, thereby reducing the stresses created in the IGU/VIGU assembly due to thermal distortions. Minimization of the thermal stresses is desirable to prevent IGU/VIGU failure in climates where significant temperature differences between adjacent lites are encountered.
The relative motion between adjacent lites in any region along the perimeter of the IGU/VIGU can be broken into two components, both of which are oriented parallel to the planes of the lites. The relative motion normal to the planes of the lites is relatively small, and is therefore not included. The two components parallel to the planes of the lites are herein defined relative to the edge seal. The motion component oriented along the length of any portion of the edge seal is herein defined as the longitudinal component and the motion component oriented at a right angle (i.e., normal) to the longitudinal component and parallel to the planes of the lites is herein defined as the lateral component. At any given point around the perimeter of the IGU/VIGU assembly, there are generally longitudinal and lateral components of relative motion between the lites at any given time. The relative motion is believed to be largest near the corners in the case of a rectangular IGU/VIGU. A need therefore exists, for an edge seal that offers compliance in both the longitudinal and lateral directions.
The edge seal for an IGU/VIGU is generally constructed of a thin sheet of material. For VIGUs, the edge seal must be hermetic, and thus is generally constructed of a thin hermetic sheet of material. The sheet material is formed in some fashion around the edge of the IGU/VIGU. The geometry of the edge seal dictates that relative motion of the lites in the longitudinal direction is largely accommodated by a shearing action of the edge seal while relative motion of the lites in the lateral direction is largely accommodated by bending of the edge seal material. Thin sheet material is relatively rigid in response to a shearing action and relatively compliant in response to a bending action. As a result, longitudinal (shear) compliance is generally more difficult to obtain than lateral (bending) compliance in an IGU/VIGU edge seal when the edge seal is formed of a thin sheet of material. A need therefore exists, for an edge seal having improved longitudinal (shear) compliance.